Outline

Modern technology has been progressed based on understanding of quantum many-body systems. In addition to the conventional study of equilibrium states, non-equilibrium dynamics plays an important role in developing further intriguing materials and advancing quantum information processing technology. In this research unit, we investigate non-equilibrium dynamics of quantum many-body systems using ultracold atomic gases. Advantages of ultracold-atom experiments are simplicity and excellent controllability of the parameters, including dimensions, of the systems. Especially, a quantum gas loaded into periodic potential generated by a laser (optical lattice) can mimic fundamental models in the strongly correlated physics, and it can be used as a platform for quantum information processing. Utilizing such systems, we investigate real-time and real-space dynamics, and also control the many-body dynamics.

Research Fields

Physics, Engineering

Keywords

Results

Dynamics of quantum spin systems using ultracold atoms in an optical lattice

Ultracold atoms in an optical lattice can emulate several fundamental models in condensed matter physics. An important example is a quantum spin system described by the Heisenberg Hamiltonian. In the ultracold-atom experiment, there exists less dissipation and less decoherence, which enable us to investigate out-of-equilibrium quantum dynamics in such spin systems.

Starting from a spin-polarized one-dimensional chain, we deterministically introduced a spin excitation by selectively flipping a single spin at the center of the chain, and tracked its subsequent dynamics with high resolution in space and time. By applying a global spin rotation, we can access not only the spatial distribution of the spin excitation but also the spin-spin correlations in the perpendicular direction. From these measurements, we evaluated spin entanglement, which is generated and transferred through the single-spin-excitation dynamics. This novel microscopic method can be used for studying dynamical evolution of quantum correlations in more complex many-body systems.

Schematics of entanglement generation and propagation via single-spin-excitation dynamics. After the spin excitation (red sphere) is introduced, entanglement propagation is observed as a function of time (orange and yellow spheres).